A while back I posted my technique for creating an animated gif out of a time series of maps. While this may have been the pinnacle of web animation circa 1997, the animated gif just didn't quite seem hip enough for this day and age.
Today I found a more modern example. This WorldKit interface, built with Flash, shows the seasonal progression of snow and land cover changes courtesy of the next generation Blue marble images. Complete with time slider, image fading and full animation controls, this interface really shines at providing an interactive experience rather than a passive visual display.